How do I find my serial number when my phone won't turn on a work?

Depending on the model of phone you have, the serial number may be on the SIM tray or back of the device. The following has more information and other ways: Find the serial number or IMEI on your iPhone, iPad or iPod touch - Apple Support

Hi

Have you still got the box or paperwork from your network provider.

Cheers

Brian 🇬-1F1E7;